Semiconductor photo-detection device and radiation detection apparatus

ABSTRACT

On the front side of an n-type semiconductor substrate  5 , p-type regions  7  are two-dimensionally arranged in an array. A high-concentration n-type region  9  and a p-type region  11  are disposed between the p-type regions  7  adjacent each other. The high-concentration n-type region  9  is formed by diffusing an n-type impurity from the front side of the substrate  5  so as to surround the p-type region  7  as seen from the front side. The p-type region  11  is formed by diffusing a p-type impurity from the front side of the substrate  5  so as to surround the p-type region  7  and high-concentration n-type region  9  as seen from the front side. Formed on the front side of the n-type semiconductor substrate  5  are an electrode  15  electrically connected to the p-type region  7  and an electrode  19  electrically connected to the high-concentration n-type region  9  and the p-type region  11 . This realizes a semiconductor photodetector and radiation detecting apparatus which can favorably suppress the occurrence of crosstalk, and restrain carriers from flowing into adjacent photodiodes even when a photodiode falls into an electrically floating state because of a breakage of a connecting point due to an initial connection error, a temperature cycle, etc.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor photodetector, and aradiation detecting apparatus equipped with the semiconductorphotodetector.

2. Related Background Art

Known as this kind of semiconductor photodetector is a backsideillumination type photodiode array in which a plurality of photodiodesare formed on one side of a semiconductor substrate, while the otherside is used as a light incident surface (see, for example, reference 1:Japanese Patent Application Laid-Open No. HEI 11-74553).

SUMMARY OF THE INVENTION

In the backside illumination type photodiode array, carriers generatedin regions other than a depletion layer in the semiconductor substratemigrate by diffusion over a long distance (from the position where theyare generated to the depletion layer). Therefore, the probability ofcarriers generated near between photodiodes flowing into their adjacentphotodiodes by migrating upon diffusion without depending on an electricfield becomes higher. As a result, crosstalk is more likely to occurbetween the photodiodes.

Meanwhile, in the backside illumination type photodiode array disclosedin the above-mentioned reference 1, a thin layer for absorbing X-rays isformed between the adjacent photodiodes. However, the thin layer inreference 1 aims at eliminating scattered X-rays, and does not takeaccount of the above-mentioned crosstalk.

In view of the foregoing, it is an object of the present invention toprovide a semiconductor photodetector and radiation detecting apparatuswhich can favorably restrain crosstalk from occurring.

The present invention provides a semiconductor photodetector comprisinga semiconductor substrate formed with a plurality of pn junction typephotodiodes on a side opposite from an incident surface for light to bedetected, wherein a pn junction region is formed between photodiodesadjacent each other in the plurality of photodiodes on the side oppositefrom the incident surface of the semiconductor substrate.

In the above semiconductor photodetector, since a pn junction region isformed between photodiodes adjacent each other in the plurality ofphotodiodes on the side opposite from the light incident surface of thesemiconductor substrate, carriers which are generated near the adjacentphotodiodes and about to flow into the adjacent photodiodes by migratingupon diffusion are drawn from the pn junction region. This eliminatescarriers which are about to flow into the adjacent photodiodes bymigrating upon diffusion, and thus can favorably restrain crosstalk fromoccurring between the photodiodes.

In the backside illumination type photodiode array, a photodiode mayfall into an electrically floating state when a certain connecting pointis damaged because of an initial connection error, a temperature cycle,etc. In this case, carriers overflowing the photodiode may flow intophotodiodes thereabout, thus hindering the latter photodiodes fromoutputting normal signals. Such a phenomenon is not mentioned at all inthe backside illumination type photodiode array disclosed in theabove-mentioned reference 1.

When a certain photodiode falls into an electrically floating statebecause of a breakage of a connecting point in the above-mentionedsemiconductor photodetector, by contrast, carriers which are about toflow into adjacent photodiodes are drawn from the pn junction region.This can favorably restrain carriers from flowing into the adjacentphotodiodes.

Preferably, the pn junction region is formed so as to surround thephotodiode as seen from the opposite side. In this case, carriers whichare about to flow into the adjacent photodiodes are surely eliminated,so that the occurrence of crosstalk can be suppressed more favorably.Also, even when a certain photodiode falls into an electrically floatingstate because of a breakage of a connecting point, carriers can morefavorably be restrained from flowing into the adjacent photodiodes.

Preferably, a high-concentration impurity semiconductor region havingthe same conductive type as that of the semiconductor substrate isformed between the pn junction region and the photodiode on the oppositeside of the semiconductor substrate. In this case, thehigh-concentration impurity semiconductor region functions to separatethe adjacent photodiodes from each other, whereby the adjacentphotodiodes are electrically separated from each other. As a result, thecrosstalk between the photodiodes can further be lowered. Also, evenwhen a certain photodiode falls into an electrically floating statebecause of a breakage of a connecting point, carriers can further berestrained from flowing into the adjacent photodiodes.

Preferably, the high-concentration impurity semiconductor region isformed so as to surround the photodiode as seen from the opposite side.This can electrically separate the adjacent photodiodes from each otherfor sure.

Preferably, an electrode electrically connected to the pn junctionregion and high-concentration impurity semiconductor region is formed onthe opposite side of the semiconductor substrate, and the electrode isconnected to a ground potential. In this case, the same electrode iscommonly used for connecting the pn junction region to the groundpotential and the high-concentration impurity semiconductor region tothe ground potential, whereby the number of electrodes can be preventedfrom increasing. The carriers drawn from the pn junction regiondisappear within the semiconductor photodetector. As a result, thecrosstalk between photodiodes is reduced. Also, even when a certainphotodiode falls into an electrically floating state because of abreakage of a connecting point, the flow of carriers into the adjacentphotodiodes can be reduced.

Preferably, a first electrode electrically connected to the pn junctionregion and a second electrode electrically connected to thehigh-concentration impurity semiconductor region are formed on theopposite side of the semiconductor substrate, whereas the first andsecond electrodes are connected to respective ground potentials whilebeing electrically insulated from each other. In this case, the pnjunction region and the high-concentration impurity semiconductor regionare electrically separated from each other within the semiconductorphotodetector. This keeps the potential on the pn junction region fromfluctuating, and thus can restrain current from flowing in because ofthe potential difference between the photodiodes and pn junction region.As a result, output signals from photodiodes are less likely to beelectrically affected, whereby a stable signal output can be realized.

Preferably, the semiconductor substrate is of a first conductive type,whereas the plurality of photodiodes and pn junction regions areconstituted by a second conductive type impurity semiconductor regionand the semiconductor substrate. Preferably, the high-concentrationimpurity semiconductor region is of the first conductive type.

The semiconductor photodetector may be configured such that the oppositeside of the semiconductor substrate is formed with respectiveelectrodes, each including a bump electrode, electrically connected tothe plurality of photodiodes; the semiconductor photodetector furthercomprising a support member formed with respective electrode pads,formed on a side facing the semiconductor substrate, corresponding tothe plurality of photodiodes; the plurality of photodiodes beingelectrically connected to the electrode pads corresponding thereto inthe support member by way of the respective bump electrodes.

The present invention provides a radiation detecting apparatuscomprising the above-mentioned semiconductor photodetector; and ascintillator, positioned on the incident surface side of thesemiconductor substrate, emitting light in response to a radiationincident thereon.

The above radiation detecting apparatus employs the above-mentionedsemiconductor photodetector, and thus can favorably suppress theoccurrence of crosstalk between photodiodes as mentioned above. Also,even when a certain photodiode falls into an electrically floating statebecause of a breakage of a connecting point, carriers can more favorablybe restrained from flowing into the adjacent photodiodes. As a result, ahigh resolution can be attained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view showing the semiconductor photodetectorin accordance with a first embodiment;

FIG. 2 is a diagram for explaining the cross-sectional structure takenalong the line II-II of FIG. 1;

FIG. 3 is a schematic plan view showing the semiconductor photodetectorin accordance with a second embodiment;

FIG. 4 is a diagram for explaining the cross-sectional structure takenalong the line IV-IV of FIG. 3;

FIG. 5 is a diagram for explaining the cross-sectional structure of amodified example of the semiconductor photodetector in accordance withthe embodiments;

FIG. 6 is a diagram for explaining the cross-sectional structure of amodified example of the semiconductor photodetector in accordance withthe embodiments;

FIG. 7 is a diagram for explaining the cross-sectional structure of theradiation detecting apparatus in accordance with an embodiment; and

FIG. 8 is a diagram for explaining the cross-sectional structure of amodified example of the semiconductor photodetector shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The semiconductor photodetector and radiation detecting apparatus inaccordance with embodiments of the present invention will be explainedwith reference to the drawings. In the explanation, constituentsidentical to each other and those having functions identical to eachother will be referred to with numerals or letters identical to eachother without repeating their overlapping descriptions.

First Embodiment

FIG. 1 is a schematic plan view showing the semiconductor photodetectorin accordance with a first embodiment. FIG. 2 is a diagram forexplaining the cross-sectional structure taken along the line II-II ofFIG. 1. In the following explanation, the incident surface for light L(on the upper side in FIG. 1) will be referred to as backside, whereasthe surface (on the lower side in FIG. 1) opposite therefrom will bereferred to as front side.

A photodiode array PD1 as a semiconductor photodetector comprises aplurality of pn junction regions 3 two-dimensionally arranged into anarray formed like a matrix with a regularity on the front side. Each ofthe pn junction regions 3 functions as a photosensitive pixel of aphotodiode.

The photodiode array PD1 is provided with an n-type (first conductivetype) semiconductor substrate 5 made of silicon (Si). Preferably, then-type semiconductor substrate 5 has a thickness of 30 to 300 μm(preferably about 100 μm) and an impurity concentration of 1×10¹² to10¹⁵/cm³.

On the front side of the n-type semiconductor substrate 5, p-type(second conductive type) regions 7 are two-dimensionally arranged intoan array formed like a matrix with a regularity. A pn junction region 3formed between each p-type region 7 and the n-type semiconductorsubstrate 5 constitutes the photosensitive pixel of each photodiode. Thep-type region 7 has an impurity concentration of 1×10¹³ to 10²⁰/cm³, anda depth of 0.05 to 20 μm (preferably about 0.2 μm).

Disposed between the p-type regions 7 adjacent each other are ahigh-concentration n-type region (separation layer) 9 as ahigh-concentration impurity semiconductor region, and a p-type region11.

The high-concentration n-type region 9 is formed by diffusing an n-typeimpurity from the front side of the substrate 5 so as to surround thep-type region 7 (photodiode) as seen from the front side. Thehigh-concentration n-type region 9 has a function of electricallyseparating adjacent photodiodes from each other. Providing thehigh-concentration n-type region 9 can electrically separate theadjacent photodiodes for sure, thereby lowering the crosstalk betweenthe photodiodes and regulating the breakdown voltage (reverse breakdownvoltage). The high-concentration n-type region 9 has an impurityconcentration of 1×10¹³ to 10²⁰/cm³, and a thickness of 0.1 to severaltens of μm (preferably about 3 μm).

The p-type region 11 is formed by diffusing a p-type impurity from thefront side of the substrate 5 so as to surround the p-type region 7(photodiode) and high-concentration n-type region 9 as seen from thefront side. A pn junction region 13 is formed between each p-type region11 and the n-type semiconductor substrate 5. Also, thehigh-concentration n-type region 9 is formed between the pn junctionregion 13 and the p-type region 7 (photodiode). The p-type region 11 hasan impurity concentration of 1×10¹³ to 10²⁰/cm³, and a depth of 0.05 to20 μm (preferably about 0.2 μm).

For the p-type regions 7 located at end portions (chip edges) of thesemiconductor substrate 5, it is not necessary to form thehigh-concentration n-type regions 9 and p-type regions 11 on the chipedge side, since there are no adjacent p-type regions 7 on the chip edgeside.

Formed on the front side of the n-type semiconductor substrate 5 is athermally oxidized film (not depicted) as a passivation film andelectrically insulating film. Formed on the backside of the n-typesemiconductor substrate 5 is an AR film (not depicted) for protectingthe backside and suppressing the reflection of light L. On the backsideof the n-type semiconductor substrate 5, the photodiode array PD1 ismade substantially flat.

Formed on the front side of the n-type semiconductor substrate 5 areelectrodes 15 electrically connected to the respective p-type regions 7.Each electrode 15 includes an electrode pad, an under-bump metal (UBM),and a bump electrode 17 (the electrode pad and UBM being undepicted).The electrode pad is made of an aluminum film, for example, and iselectrically connected to its corresponding p-type region 7 through acontact hole formed in the thermally oxidized film. The UBM is formed,for example, by plating an electrode conductor with Ni and Au insuccession. The bump electrode 17 is made of solder, and is formed onthe UBM.

Electrodes 19 electrically connected to the high-concentration n-typeregions 9 and p-type regions 11 are formed on the front side of then-type semiconductor substrate 5. Each electrode 19 includes anelectrode conductor 21, a UBM (not depicted), and a bump electrode 23.The electrode conductor 21 is made of an aluminum film, for example, andis electrically connected to the high-concentration n-type region 9 andp-type region 11 through a contact hole formed in the thermally oxidizedfilm. As is also illustrated by FIG. 2, the electrode conductor 21 isformed so as to cover the high-concentration n-type region 9 and p-typeregion 11 as seen from the front side of the n-type semiconductorsubstrate 5. The UBM is formed, for example, by plating the electrodeconductor 21 with Ni and Au in succession. The bump electrode 23 is madeof solder, and is formed on the UBM. The electrode 19 is connected tothe ground potential.

In the photodiode array PD1, the anode extraction of each photodiode isrealized by the electrode 15, whereas the cathode extraction is realizedby the electrode 19. Also, in the photodiode array PD1, depletion layers25 are formed in boundaries of the pn junction regions 3, 13.

When the light L to be detected is incident on the photodiode array PD1from the backside, each photodiode generates a carrier corresponding tothe incident light. The photocurrent caused by thus generated carrier istaken out from the electrode 15 (bump electrode 17) connected to thep-type region 7. As is also illustrated by FIG. 2, the output from theelectrode 15 is connected to the inverting input terminal of adifferential amplifier. The non-inverting input terminal of thedifferential amplifier 27 is connected to the ground potential in commonwith the electrode 19.

FIG. 8 is a diagram for explaining the cross-sectional structure of amodified example of the semiconductor photodetector shown in FIG. 2.Here, a photodiode array PD5 as a semiconductor photodetector comprises,in addition to a semiconductor substrate 5, a wiring board 80 as asupport member for supporting the semiconductor substrate 5.

Formed on the front side of the semiconductor substrate 5 are electrodes15 electrically connected to their corresponding p-type regions 7 asmentioned above. In the example shown in FIG. 8, each electrode 15 isconstituted by an electrode pad 15 a, a UBM 15 b, and a bump electrode17. Formed on the front side of the semiconductor substrate 5 areelectrodes 19 electrically connected to their correspondinghigh-concentration n-type regions 9 and p-type regions 11. In theexample shown in FIG. 8, each electrode 19 is constituted by anelectrode pad 19 a, a UBM 19 b, and a bump electrode 23.

On the side of wiring board 80 facing the semiconductor substrate 5,with respect to the electrodes 15, 19 on the semiconductor substrate 5,electrode pads 81 are formed so as to correspond to the p-type regions 7(photodiodes). As shown in FIG. 8, the p-type regions 7 of thesemiconductor substrate 5 are electrically connected to theircorresponding electrode pads 81 of the wiring board 80 by way of thebump electrodes 17 of the electrodes 15, respectively.

On the side of wiring board 80 facing the semiconductor substrate 5,electrode pads 82 are formed so as to correspond to the respectivehigh-concentration n-type regions 9 and p-type regions 11. As shown inFIG. 8, the high-concentration n-type regions 9 and p-type regions 11 ofthe semiconductor substrate 5 are electrically connected to theircorresponding electrode pads 82 of the wiring board 80 by way of thebump electrodes 23 of the electrodes 19.

In the first embodiment, as in the foregoing, the p-type regions 11 (pnjunction regions 13) are formed between p-type regions 7 (photodiodes)adjacent each other among a plurality of p-type regions 7 on the frontside of the n-type semiconductor substrate 5. As a consequence, evenwhen a carrier C occurs in the vicinity of the adjacent p-type regions7, in regions other than the depletion layers 25 in the n-typesemiconductor substrate 5, the carrier C that is about to flow into theadjacent p-type regions 7 by migrating upon diffusion is drawn from thep-type region 11 as indicated by arrow A in FIG. 2. As a result, thecarrier C that is about to flow into the adjacent p-type regions 7 bymigrating upon diffusion is eliminated, whereby crosstalk can favorablybe restrained from occurring between the p-type regions 7.

In the backside illumination type photodiode array PD1 in which thelight L is incident on the backside, as FIG. 8 exemplifies itsconnecting structure, a bump connection employing bump electrodes ispreferably used in the connection with respect to a support member suchas wiring board. In such a configuration using a bump connection, aconnecting point may be damaged because of an initial connection error,a temperature cycle, etc., whereby a p-type region 7 (photodiode) mayfall into an electrically floating state.

In the photodiode array PD1 configured as mentioned above, by contrast,even when a certain p-type region 7 falls into an electrically floatingstate because of a breakage of a connecting point due to an initialconnection error, a temperature cycle, etc., carriers overflowing thep-type region 7 are drawn from the p-type region 11. This can favorablyrestrain carriers from flowing into the adjacent p-type regions 7. Thisis also effective in cases employing connecting structures other thanthe bump connection.

In the first embodiment, each p-type region 11 is formed so as tosurround its p-type region 7 as seen from the backside of the n-typesemiconductor substrate 5. This certainly eliminates the carrier C thatis about to flow into the adjacent p-type regions 7 by migrating upondiffusion, and thus can suppress the occurrence of crosstalk morefavorably.

Also, even when a certain p-type region 7 falls into an electricallyfloating state because of a breakage of a connecting point, carriersoverflowing the p-type region 7 are drawn from the p-type region 11surrounding the p-type region 7. This can further favorably restraincarriers from flowing into adjacent p-type regions 7.

In the first embodiment, the high-concentration n-type regions 9 areformed between the p-type regions 7 and 11 on the front side of then-type semiconductor substrate 5. This can electrically separate theadjacent p-type regions 7 from each other, thereby further lowering thecrosstalk between the p-type regions 7. Also, even when a certainphotodiode falls into an electrically floating state because of abreakage of a connecting point, the flow of carriers into adjacentphotodiodes can further be reduced.

In the first embodiment, each high-concentration n-type region 9 isformed so as to surround its corresponding p-type region 7 as seen fromthe backside of the n-type semiconductor substrate 5. This canelectrically separate the adjacent p-type regions 7 for sure.

In the first embodiment, the electrodes 19 electrically connected to thehigh-concentration n-type regions 9 and p-type regions 11 are formed onthe front side of the n-type semiconductor substrate 5, and areconnected to a ground potential. As a consequence, the same electrodecan commonly be used for connecting both the p-type region 11 andhigh-concentration n-type region 9 to the ground potential, therebypreventing the number of electrodes from increasing. In this case, thecarrier C drawn from the p-type region 11 disappears within thephotodiode array PD1.

In the first embodiment, the p-type regions 11 can be formed in the sameprocess as with the p-type regions 7. In this case, the process ofmaking the photodiode array PD1 will not be complicated.

Second Embodiment

FIG. 3 is a schematic plan view showing the semiconductor photodetectorin accordance with a second embodiment. FIG. 4 is a diagram forexplaining the cross-sectional structure taken along the line IV-IV ofFIG. 3. The photodiode array PD2 in accordance with the secondembodiment differs from the photodiode array PD1 in accordance with thefirst embodiment in terms of electrode structures of high-concentrationn-type regions 9 and p-type regions 11.

Formed on the front side of the n-type semiconductor substrate 5 areelectrodes 31 (corresponding to the second electrode) electricallyconnected to their corresponding high-concentration n-type regions 9.Each electrode 31 includes an electrode conductor 33, a UBM (notdepicted), and a bump electrode 35. The electrode conductor 33 is madeof an aluminum film, for example, and is electrically connected to itscorresponding high-concentration n-type region 9 through a contact holeformed in a thermally oxidized film. As is also shown in FIG. 4, theelectrode conductor 33 is formed so as to cover the high-concentrationn-type region 9 as seen from the front side of the n-type semiconductorsubstrate 5. The UBM is formed, for example, by plating the electrodeconductor 33 with Ni and Au in succession. The bump electrode 35 is madeof solder, and is formed on the UBM. The electrode 31 is connected tothe non-inverting input terminal of a differential amplifier 27, whereasa middle part of a lead between the electrode 31 and the non-invertinginput terminal of the differential amplifier 27 is connected to a groundpotential. Therefore, the electrode 31 and the non-inverting inputterminal of the differential amplifier 27 are connected to the commonground potential.

Formed on the front side of the n-type semiconductor substrate 5 areelectrodes 41 (corresponding to the first electrode) electricallyconnected to their corresponding p-type regions 11. Each electrode 41includes an electrode conductor 43, a UBM (not depicted), and a bumpelectrode 45. The electrode conductor 43 is made of an aluminum film,for example, and is electrically connected to its corresponding p-typeregion 11 through a contact hole formed in the thermally oxidized film.As is also shown in FIG. 2, the electrode conductor 43 is formed so asto cover its p-type region 11 as seen from the front side of the n-typesemiconductor substrate 5. The UBM is formed, for example, by platingthe electrode conductor 43 with Ni and Au in succession. The bumpelectrode 45 is made of solder, and is formed on the UBM. The electrodes41 are electrically insulated from the electrodes 31. While beingelectrically insulated from the electrodes 31, the electrodes 41 areconnected to a ground potential different from that of the electrodes 31on the outside of the photodiode array PD2.

As explained in the foregoing, a carrier C which is about to flow intoadjacent p-type regions 7 by migrating upon diffusion is drawn from ap-type region 11 in the second embodiment as in the first embodiment.This eliminates the carrier that is about to flow into the adjacentp-type regions 7 by migrating upon diffusion, and thus can favorablyrestrain crosstalk from occurring between the p-type regions 7.

Also, even when a certain p-type region 7 falls into an electricallyfloating state because of a breakage of a connecting point due to aninitial connection error, a temperature cycle, etc., carriersoverflowing the p-type region 7 are drawn from the p-type region 11.This can favorably restrain carriers from flowing into the adjacentp-type regions 7.

Also, in the second embodiment, the electrodes 31 electrically connectedto their corresponding high-concentration n-type regions 9 and theelectrodes 41 electrically connected to their corresponding p-typeregions 11 are formed on the front side of the n-type semiconductorsubstrate 5. While being electrically insulated from each other, theelectrodes 31 and 41 are connected to the respective ground potentialsdifferent from each other. In this configuration, the high-concentrationn-type regions 9 and p-type regions 11 are electrically separated fromeach other within the photodiode array PD2. As a consequence, even whenthe ground potential varies, for example, the potential of the p-typeregions 11 does not fluctuate, whereby currents can be restrained fromflowing in because of the potential difference between the p-typeregions 7 and 11. As a result, output signals from the p-type regions 7are less likely to be electrically affected (by noise superposition),whereby a stable signal output can be realized.

In the second embodiment, the p-type regions 11 can be formed in thesame process as with the p-type regions 7, whereas the electrodes 41 canbe formed by the same process as with the electrodes 31 and 15. In thiscase, the process of making the photodiode array PD2 will not becomplicated.

Since the electrodes 31 and 41 are electrically insulated from eachother, it is easy to apply a reverse bias voltage in the photodiodearray PD2. Therefore, when an integrating amplifier is used fordetecting signals, low signals can easily be detected.

With reference to FIGS. 5 and 6, modified examples of the semiconductorphotodetector in accordance with these embodiments will be explained.FIGS. 5 and 6 are diagrams for explaining the respective cross-sectionalstructures of modified examples of the semiconductor photodetector inaccordance with the above-mentioned embodiments.

The photodiode array PD3 as a semiconductor photodetector shown in FIG.5 differs from the photodiode array PD1 in accordance with the firstembodiment in terms of the form of the n-type semiconductor substrate 5.The photodiode array PD4 as a semiconductor photodetector shown in FIG.6 differs from the photodiode array PD2 in accordance with the secondembodiment in terms of the form of the n-type semiconductor substrate 5.

In each of the photodiode arrays PD3, PD4, recesses 51 are formed inrespective areas corresponding to the pn junction regions 3 (p-typeregions 7) on the backside of the n-type semiconductor substrate 5. As aconsequence, in areas corresponding to spaces between the adjacentp-type regions 7, protrusions 53 are formed so as to surround therespective areas corresponding to the p-type regions 7.

In the photodiode arrays PD3, PD4, as in the above-mentionedembodiments, carriers C which are about to flow into the adjacent p-typeregions 7 by migrating upon diffusion are eliminated, whereby theoccurrence of crosstalk between the p-type regions 7 can favorably besuppressed.

Also, even when a certain p-type region 7 falls into an electricallyfloating state because of a breakage of a connecting point due to aninitial connection error, a temperature cycle, etc., carriersoverflowing the p-type region 7 are drawn from the p-type region 11.This can favorably restrain carriers from flowing into adjacent p-typeregions 7.

The photodiode arrays PD3, PD4 can shorten the distance from the surfaceof the n-type semiconductor substrate 5 (i.e., the incident surface forlight L) to the pn junction region 3, while keeping a mechanicalstrength. Since the distance from the surface of the n-typesemiconductor substrate 5 to the pn junction region 3 is short, thecarriers C generated in the n-type semiconductor substrate 5 arerestrained from recombining in the process of migrating to the pnjunction region 3.

With reference to FIG. 7, the radiation detecting apparatus inaccordance with an embodiment will now be explained. FIG. 7 is a diagramfor explaining the cross-sectional structure of the radiation detectingapparatus in accordance with this embodiment.

This radiation detecting apparatus RD comprises a scintillator 61adapted to emit light in response to a radiation incident thereon, andthe above-mentioned photodiode array PD1. In place of the photodiodearray PD1, the photodiode arrays PD2 to PD4 may be used as well.

The scintillator 61 is positioned on the backside of the photodiodearray PD1. The light emitted from the scintillator 61 enters thephotodiode array PD1 from the backside thereof. The scintillator 61 isbonded to the backside of the photodiode array PD1. For bonding thescintillator 61 and the photodiode array PD1 together, alight-transparent resin (e.g., epoxy resin or acrylic resin) can beused.

The radiation detecting apparatus RD comprises the photodiode array PD1,thereby favorably suppressing the occurrence of crosstalk between thep-type regions 7. Also, even when a certain photodiode falls into anelectrically floating state because of a breakage of a connecting pointdue to an initial connection error, a temperature cycle, etc., carriersare favorably restrained from flowing into adjacent photodiodes. Thiscan achieve a high resolution.

The present invention is not restricted to the above-mentionedembodiments. For example, though the present invention is employed inphotodiode arrays in which a plurality of pn junctions aretwo-dimensionally arranged into a matrix with a regularity in theabove-mentioned embodiments, they are not restrictive. The presentinvention can also be employed in photodiode arrays in which pnjunctions are arranged one-dimensionally.

The photodiode arrays PD1 to PD4 and radiation detecting apparatus RD inaccordance with the above-mentioned embodiments are suitable for X-rayCT apparatus.

The present invention can provide semiconductor photodetectors andradiation detecting apparatus which can favorably restrain crosstalkfrom occurring. Also, the present invention can provide semiconductorphotodetectors and radiation detecting apparatus in which, even when acertain photodiode falls into an electrically floating state because ofa breakage of a connecting point due to an initial connection error, atemperature cycle, etc., carriers are favorably restrained from flowinginto adjacent photodiodes.

1-14. (canceled)
 15. A semiconductor photodetector comprising asemiconductor substrate formed with a plurality of pn junction typephotodiodes on a side of the semiconductor substrate opposite from anincident surface of the semiconductor substrate for receiving light tobe detected; wherein, on the side of the semiconductor substrateopposite from the incident surface, a separate region including a pnjunction, which is separate from the photodiodes, is formed betweenphotodiodes adjacent each other in the plurality of photodiodes, and ahigh-concentration impurity semiconductor region having the sameconductivity type as that of the semiconductor substrate is formedbetween the separate region and each of the photodiodes adjacent theseparate region, the separate region is disposed so as to be sandwichedbetween the high-concentration impurity semiconductor regions, and thehigh-concentration impurity semiconductor region is formed so as tosurround the photodiode as seen from the opposite side.
 16. Asemiconductor photodetector according to claim 15, wherein the separateregion is formed so as to surround at least one of the photodiodes asseen from the opposite side.
 17. A semiconductor photodetector accordingto claim 15, wherein the opposite side of the semiconductor substrate isformed with respective electrodes, each including a bump electrode,electrically connected to the plurality of photodiodes, wherein thesemiconductor photodetector further comprises a support member formedwith respective electrode pads, formed on a side facing thesemiconductor substrate, corresponding to the plurality of photodiodes,and the plurality of photodiodes are electrically connected to theelectrode pads corresponding thereto in the support member by way of therespective bump electrodes.
 18. A semiconductor photodetector accordingto claim 15, wherein an electrode electrically connected to the separateregion and high-concentration impurity semiconductor region is formed onthe opposite side of the semiconductor substrate, and wherein anelectrode conductor included in the electrode is formed so as to coverthe separate region and the high-concentration impurity semiconductorregions disposed so as to sandwich the separate region.
 19. Asemiconductor photodetector according to claim 15, wherein a firstelectrode electrically connected to the separate region and a secondelectrode electrically connected to the high-concentration impuritysemiconductor region are formed on the opposite side of thesemiconductor substrate, and wherein the first and second electrodes areelectrically insulated from each other.
 20. A semiconductorphotodetector according to claim 15, wherein the semiconductor substrateand high-concentration impurity semiconductor region are of a firstconductivity type, and wherein the thickness of the high-concentrationimpurity semiconductor region is greater than the depth of a secondconductivity type impurity semiconductor region constituting theseparate region with the semiconductor substrate.
 21. A semiconductorphotodetector according to claim 15, wherein a protrusion portion isformed on the incident surface side of the semiconductor substrate, andwherein, on the side of the semiconductor substrate opposite from theincident surface, the separate region and the high-concentrationimpurity semiconductor regions disposed so as to sandwich the separateregion are formed in a region corresponding to the protrusion portion.22. A radiation detecting apparatus comprising the semiconductorphotodetector according to claim 15; and a scintillator, positioned onthe incident surface side of the semiconductor substrate, emitting lightin response to a radiation incident thereon.